The present invention relates to lead pipes used for guiding proper directional advance of an underground piping run such as for a fresh water or a sewer line and, more particularly, to a lead pipe arrangement wherein light blocking and light absorbing means are provided within at least some of the lead pipes to prevent unwanted light interference with a light detecting transit located at the rear of the lead pipe arrangement and which detected light is used for determining if lead pipe run and hence, piping run lay down has correct direction.
In past propulsion-type piping devices, a propulsion machine is used to rotate and propel a lead pipe configuration, which has a direction correcting head. As propulsion proceeds, lead pipes are added on from a rear of the configuration in endwise succession form as needed and until the pipe lay down destination is reached. These lead pipes are used as guides for propelling an excavation screw and piping being laid down.
If there is an error in the direction of the lead pipes, the direction correcting head is used to correct the direction. A light source is located at the rear of the direction correcting head in order to determine whether the direction of propulsion matches the planned direction. The light from this light source passes through the hollow center of the lead pipes and is detected by a transit, and the lead pipe advance direction is adjusted based on this.
In the underground piping device described above, the light source arranged at the rear of the direction correcting head passes through the lead pipe hollow center, thus allowing some of the light reflect against the inside surface of the lead pipe. This results in situations where the light from the light source could not be detected accurately by the transit. The lead pipes are generally made of steel for strength reasons, and this causes irregular reflections. When pipes are put in storage after use, oil is applied as a rust-prevention measure, and this also leads to irregular reflections. These irregular reflections can affect the accuracy of the light detection and correction procedure greatly.